lvls_reorder leaves values as they are, but changes the order.
lvls_revalue changes the values of existing levels; there must
be one new level for each old level.
lvls_expand expands the set of levels; the new levels must
include the old levels.
Usage
lvls_reorder(f, idx, ordered = NA)
lvls_revalue(f, new_levels)
lvls_expand(f, new_levels)
Arguments
- f
A factor (or character vector).
- idx
A integer index, with one integer for each existing level.
- ordered
A logical which determines the "ordered" status of the
output factor. NA preserves the existing status of the factor.
- new_levels
A character vector of new levels.
Details
These functions are less helpful than the higher-level fct_ functions,
but are safer than the very low-level manipulation of levels directly,
because they are more specific, and hence can more carefully check their
arguments.
Examples
f <- factor(c("a", "b", "c"))
lvls_reorder(f, 3:1)
#> [1] a b c
#> Levels: c b a
lvls_revalue(f, c("apple", "banana", "carrot"))
#> [1] apple banana carrot
#> Levels: apple banana carrot
lvls_expand(f, c("a", "b", "c", "d"))
#> [1] a b c
#> Levels: a b c d
